In recent years, a light emitting device using a light emitting element represented by an electroluminescent (EL) element and the like has been developed in substitution for a liquid crystal display (LCD) comprising a pixel using a liquid crystal element as a light emitting element. These light emitting devices are expected to be widely used as a display of a portable phone and a display device by taking advantages of high image quality, wide viewing angle, thin design without a need of backlight, lightweight and the like due to a light emission type.
Furthermore, a portable information terminal is demanded to have a high-value added because of the diversification of applications and is recently provided with a sub-display on the back of a normal display.